The majority of butterflies, if transferred to pill boxes from the net, settle down quietly. In this way they may be taken to one's home and there placed, boxes and all, into the ammonia jar, a simple but very effective contrivance. To start one of these lethal chambers, procure a good sized pickle jar, one of the brown earthenware kind, holding about 2 gallons. At the bottom put in several layers of stout blotting-paper, and have ready a covering for the mouth of the jar. This covering may be of skin, waterproof-apron material, or even thick brown paper. Before turning the boxes into the jar, lift up the blotting-paper, drop in about half a teaspoonful of strong liquid ammonia (·880) and replace blotting-paper. Directly the boxes are in the jar, put on cover and tie it down securely. If brown paper is used, a piece of pasteboard should be put over it and a weight on top of that. Suffocation takes place directly the gas reaches the insect, but it often happens that one or more of the boxes exclude the gas longer than others. At the end of half an hour all may be removed, but the insects will not hurt in any way if left in all night. The best kind of boxes for field work are those known as "glass bottomed," as in these the captives can be examined and, if not wanted, may be set free. It is always better to retain only those specimens that we know are really useful, rather than to incur the necessity of throwing away insects after we have deprived them of life. [Sidenote: Pinning.] If butterflies are pinned on the spot, a collecting box will be required, and the most useful and convenient is one of an oval shape. This should be made of zinc, and lined with cork that is held in place by zinc clips. The cork should be kept damp when in use, and the water used for damping should have a few drops of carbolic acid mixed with it so as to prevent the formation of mould. Insects may remain in such a box for several days without injury. This box will also be useful for relaxing specimens that have been badly set, or have been simply pinned during the busy season. In the matter of pins, it is not altogether easy to make suggestions. There are, perhaps, only two makers in this country of entomological pins, and each of these supplies a large number of sizes. The selection of suitable pins will largely depend on the method of setting adopted. Black pins are, however, the best for butterflies, and are now used almost exclusively.